Rebellion Studios really has no chance of winning this by any means except attempting simply drag the matter out. Trademarks come in four strengths:
1. Generic: These have no protection so you can't have Milk brand milk
2. Description: These have weak protection, so a game about a rebellion being named Rebellion.
3. Arbitrary: These can have very strong protection as long as you can show that the term has nothing to do with the market your products are in, but it does not give you rights to anything that is considered a generic use of the term. Apple Computers falls into this category because apples have nothing to do with computers excluding of course, the arbitrary brand of computers known as Apples. That does not however give Apple any right to sue Granny Smith Apples as that mark exists in a completely different market where the term is descriptive.
4. Fanciful: If you make up a word and use that as you're name you're very well protected. This means that Exxon could come after you if you tried to sell Exxon Oranges even though Exxon certainly doesn't sell oranges.
In this case Rebellion Studio's name is arbitrary, but it makes the mistake of using a word that has already been associated with numerous gaming titles, such as "Star Wars: Rebellion". They would be hard pressed to show that their studio's name acquired a strong secondary meaning that the use of the descriptive term "rebellion" somehow damages, as such they have no case.
Also kudos on the captcha for this wonderful insight, "reduplicated phrases", well said.